Customers cannot checkout

In the last week we have having massive problems with customers unable to checkout. The symptoms are always the same. They login or register try to pay using a credit/debit card put in their payment details, the transaction goes off to the 3DS page and the transaction is authorised by the card company but... the customer is returned to the login page and the items are still in their shopping basket.

Most customers report that they are using Chrome. Obviously only a fraction of the customers who experience this problem call in it is costing us a huge amount of lost orders. I cannot replicate the problem, I have tried all browsers on PC and Mac I am starting to wonder if this is card problem i.e. each 3DS page is different and maybe it breaks the link but in any even I don't understand why the customer is being returned to the Login Page.